Safety mechanism for elevators



1. HOFFER. SAFETY MECHANISM FOR EL'EVATORS.

APPLICATION FILED JAN. 10, 1920- 1 ,396,751 I Patented Nov. 15, 1921fFIBJ- INVENTOI wmazazs @ZfWM TTPATJENT OFFICE.

OHN HOFFER, or MARiANNA, Przmvsvr.Vania.

SAFETY MECHANISM FOR ELEVATORS.

Specification of Letters Patent. Patented Nay. 15, 1921.

Application filed January 10, 1920. Serial No. 350,558.

To all whom itmag concern:

Beit known that I, JOHN Horrnn, residing at Marianna, in the county ofWashington and State of Pennsylvania, a subject of the former Kingdom ofHungary, in the former Austro-Hungarian Empire, have inventedordiscovered certain new and useful Improvements in Safety Mechanism forElevators, of which improvements the following is a specification.

My invention relatesto improvements in safety mechanism applied toelevator cars and cagessuch as those used in mines and in oflicebuildings, cars raised and lowered by cable for carrying men andvehicles upon steep hill sides, and the like. The object is to eliminateand overcome a difficulty in the proper operation of mechanisms of thissort which otherwise comes about in service, in consequence ofelongation of the car-sustaining cable.

In the accompanying drawings, Figure 1 shows in elevation an elevatorinstallation in which my invention is applied; Fig. 2 is a similar viewof one car alone, showing in specific form a detail presently to be.described.

Two cars 1, 1 are suspended in their shafts by cables 2, 2, and thecables are, it will be understood, parts of a continuous whole, to theend that the two cars are sustained in counterbalance, one against theother-an arrangement peculiarly useful in mines and upon inclined planesof city transportation, and an arrangement which requires a minimumamount of power to effect elevation. a The safety device is one which isoperated by a second cable 9, upon which, on the parting of thecar-sustaining cable 2, the weight of the car comes. Thereby the safetydevice is operated. The invention is not conditioned. upon any specificform of safety device; it is requisite to the invention only that. thesafety device he operable by tension upon a cable; beyond this, theparticular construction may be whatever is preferred. In the drawings Ihave shown the safety device of my now pending application for LettersPatent, Serial No. 286,665, filed April 1, 1919, wherein the tensionthrown upon cable 9, when the weight of a car is imposed upon it, turnsa drum 8 and turning of the drum is communicated to shafts 11 which inturning cause clamping members 10, arranged in pairs upon opposite sidesof posts 3, to come to post-engaging positions and so to arrest thefalling of a car. But it will be understood that the safety device of myPatent No. 1,324,451 might be employed, or any other safety devicehaving thecharacteristic already definedthat, namely, of operating undertension exerted through a cable.

Ordinarily in an installation which includes two cars hung incounterbalance the cable for operating the safety device extends fromone car, over sheavesat the top of the shaft or runway, to the othercar; the safety cable so arranged is normally slack. In case thecar-sustaining cable breaks, the weight of the car is at once imposed onthe safety cable, the safety cable is drawn taut, and the safety deviceoperates, to arrest the car as it begins to fall.

A difliculty lies in this: that, as the elevator continues in use, thecar-sustaining cable is liable to stretch, until the slack in thesafety-device cable is taken up, and the safety device comes into actioninopportunely.

My invention consists in carrying the cable 9, through which the safetydevice is operated. from one car upward to the top o the shaft andthence downward to the other car. and. in forming in this cable,intermediate its length, a loo 12, depending from the top of the shaft.In this loop I hang a weight 13, and adjacent and above the weight Iplace a stop 14. The connection of the cable 9 to the safety devices ofthe two cars is such that the safety devices remain in normal inactiveposition under the minor tension exerted. through the cable 9 by theweight 13. vbut under the major tension presently to be more fullyindicated which, upon parting of cable 2 is exerted through cable 9. thesafety devices will come into action and. both cars will by their safetydevices be secured in the shafts, against the possibility of falling.

One specificway of accomplishing the end just described is shown in Fig.2. The cable 9 is. at the end where it engages drum 8, slackened by line15, which hitches cable 9 at a point remote from the drum directly tothe car. Line 15 is relatively weak; it is sufiiciently strong tosustain weight 13 under all conditions of use, but in case cable 2 partsand one car or both begin to fall, immediately loop 12 in cable 9 willshorten and weight 13 will abut upon stop 14. Thereupon the tensionexerted upon lines-15 will break them both and both the drums Softhesafety devices will turn, both safety devices will operate and both carswill be secured in Whatever position they chance to be found in theshafts. All this will come about before the broken-away car has byfalling gained any considerable momentum.

Thus it will. be appreciated that cable 9 is held by Weight 13 alwaystaut, that loop 12 by growing shorter makes compensation forstretchingof the car-sustaining cable: the :safety device can never beoperated by the mere stretching of the car-sustaining cable; but,'incase cable 2 breaks, the safety devices will be operated on theengagement of weight 13 withstop 14% by the consequent sudden tensionimposed on cable 9.

I claim as my invention:

In a safety device for elevator cars and cages the combination of twocars hung in cminterbalance, a safety cable extending from car to carand hanging intermediate its length in a loop susceptible to elongation.and shortening, a tension-operated safety mechanism borne by one ofsaid ears, to which safety mechanism said safety cable is connected,means rendered ineffective under major stress, relieving said safetymechanism under normal conditions of the weight of said looped safetycable, and a stop limitin c the extent to which the loop in said safetycable may shorten, substantially .as described.

In testimony whereof I have hereunto set my hand.

JOHN HOFFER.

lVitnesses FRANCIS J. ToimssoN, FnANcis J. BEVILACFUA.

